EARLY DEVONIAN FUNGI - A BLASTOCLADALEAN FUNGUS WITH SEXUAL REPRODUCTION

In this paper we describe a fossil fungus-Paleoblastocladia milleri ge n. et sp. nov.-from the 400 million-year-old Early Devonian Rhynie che rt that shares numerous features with modern zoosporic fungi placed in the order Blastocladiales. The fungus occurs in tufts that arise from stomata or between the cuticle and epidermis of Aglaophyton major axe s. Thallus development begins from an irregular bipolar basal cell tha t produces a system of intramatrical rhizoids and clavate-shaped extra matrical, nonseptate hyphae. These hyphae develop into two types of ma ture thalli. Sporothalli are characterized by several orders of dichot omous branching and the production of terminal, globose zoosporangia, as well as thick-walled, pitted resting sporangia. On separate dichoto mously branched thalli (gametothalli) are terminal chains of two or th ree gametangia, in which the terminal one is slightly larger. Despite the fact that all of the reproductive organs contain either zoospores or gametes, none show evidence of discharge papillae. The fossil fungu s is compared with extant members of the Blastocladiales, and the pres ence of sexual reproduction is discussed.